Solved! hp pavilion

Solution
On many devices, if you fully disconnect the attached display, they won't work. However, if you are hooking up an external display, there should be no need to try and disconnect the attached one.

Even rebooting the computer should go straight back to using the external monitor.

Have you tried that? Just attaching the external and seeing if it works fine, even after a reboot?
On many devices, if you fully disconnect the attached display, they won't work. However, if you are hooking up an external display, there should be no need to try and disconnect the attached one.

Even rebooting the computer should go straight back to using the external monitor.

Have you tried that? Just attaching the external and seeing if it works fine, even after a reboot?
 
Solution